论文标题
动态加速覆盖时间
Dynamically accelerated cover times
论文作者
论文摘要
在表征图形或晶格的随机探索的可观察到的覆盖时间,即访问每个站点的时间,继续引起广泛的兴趣。通过映射(无间距)优惠券收集器问题,可以获得有关覆盖时间的许多见解,这相当于忽略时空的相关性,以及早期的猜想,即最近证明,在$ d \ egq 3 $中,大型晶格上常规随机步行的限制性覆盖时间分布收敛于gumbel分布。此外,许多数学和数值研究表明,牙胶普遍性对随机搜索过程的\ textIt {fastial}特征的修改(例如\ \引入持久性和/或间歇性,或更改图形拓扑)的修改(例如\ \引入持久性和/或间歇性)。在这里,我们研究了牙胶普遍性的鲁棒性,即搜索的\ textit {时间}特征的动态修改,特别是通过允许随机助行器访问先前未探索的站点时“加速”或“减速”。我们通过将覆盖时间的统计数据与$ 1/f^α$高斯信号的粗糙度联系起来来概括上述映射,从而猜测,Gumbel分布不过是一个覆盖时间分布的家族之一,从高斯(Gaussian for Gaussian for Gaussian for Gaussian for Gaussian for Gaussian for Gaussian for Gaussian)高度加速,到高度减速的封面。虽然我们的猜想是通过系统的蒙特卡洛模拟在维度上确认的$ d> 3 $,但我们在$ d = 3 $中加速的结果挑战了当前对相关性在覆盖时间问题中的作用的理解。
Among observables characterising the random exploration of a graph or lattice, the cover time, namely the time to visit every site, continues to attract widespread interest. Much insight about cover times is gained by mapping to the (spaceless) coupon-collector problem, which amounts to ignoring spatio-temporal correlations, and an early conjecture that the limiting cover time distribution of regular random walks on large lattices converges to the Gumbel distribution in $d \geq 3$ was recently proved rigorously. Furthermore, a number of mathematical and numerical studies point to the robustness of the Gumbel universality to modifications of the \textit{spatial} features of the random search processes (e.g.\ introducing persistence and/or intermittence, or changing the graph topology). Here we investigate the robustness of the Gumbel universality to dynamical modification of the \textit{temporal} features of the search, specifically by allowing the random walker to "accelerate" or "decelerate" upon visiting a previously unexplored site. We generalise the mapping mentioned above by relating the statistics of cover times to the roughness of $1/f^α$ Gaussian signals, leading to the conjecture that the Gumbel distribution is but one of a family of cover time distributions, ranging from Gaussian for highly accelerated cover, to exponential for highly decelerated cover. While our conjecture is confirmed by systematic Monte Carlo simulations in dimensions $d > 3$, our results for acceleration in $d=3$ challenge the current understanding of the role of correlations in the cover time problem.